Difference between Raster Image and Vector Based Images

Hi All,
In differentiating the two kinds of images what i conclude is "Vector based images are mathematical images - this implies that these are image format used by computers. This is true because a raster image has definition defined pixel by pixel.
For a better understanding pls go through the following link:
http://www.nw-media.com/photography-articles/31/raster-vs-vector/